Fall back to using pk/ui from orig table if new table del index uses cols that no longer exist in orig table.

bin/pt-online-schema-change

@@ -8370,19 +8370,74 @@ sub main {
    # Find a pk or unique index to use for the delete trigger.  can_nibble()
    # above returns an index, but NibbleIterator will use non-unique indexes,
    # so we have to do this again here.
+   {
       my $indexes = $new_tbl->{tbl_struct}->{keys}; # brevity
       foreach my $index ( $tp->sort_indexes($new_tbl->{tbl_struct}) ) {
          if ( $index eq 'PRIMARY' || $indexes->{$index}->{is_unique} ) {
-         PTDEBUG && _d('Delete trigger index:', Dumper($index));
+            PTDEBUG && _d('Delete trigger new index:', Dumper($index));
             $new_tbl->{del_index} = $index;
             last;
          }
       }
+      PTDEBUG && _d('New table delete index:', $new_tbl->{del_index});
+   }
+
+   {
+      my $indexes = $orig_tbl->{tbl_struct}->{keys}; # brevity
+      foreach my $index ( $tp->sort_indexes($orig_tbl->{tbl_struct}) ) {
+         if ( $index eq 'PRIMARY' || $indexes->{$index}->{is_unique} ) {
+            PTDEBUG && _d('Delete trigger orig index:', Dumper($index));
+            $orig_tbl->{del_index} = $index;
+            last;
+         }
+      }
+      PTDEBUG && _d('Orig table delete index:', $orig_tbl->{del_index});
+   }
+
    if ( !$new_tbl->{del_index} ) {
       die "The new table $new_tbl->{name} does not have a PRIMARY KEY "
         . "or a unique index which is required for the DELETE trigger.\n";
    }
 
+   # Determine whether to use the new or orig table delete index.
+   # The new table del index is preferred due to
+   # https://bugs.launchpad.net/percona-toolkit/+bug/1062324
+   # In short, if the chosen del index is re-created with new columns,
+   # its original columns may be dropped, so just use its new columns.
+   # But, due to https://bugs.launchpad.net/percona-toolkit/+bug/1103672,
+   # the chosen del index on the new table may reference columns which
+   # do not/no longer exist in the orig table, so we check for this
+   # and, if it's the case, we fall back to using the del index from
+   # the orig table.
+   my $del_tbl = $new_tbl; # preferred
+   my $new_del_index_cols  # brevity
+      = $new_tbl->{tbl_struct}->{keys}->{ $new_tbl->{del_index} }->{cols};
+   foreach my $new_del_index_col ( @$new_del_index_cols ) {
+      if ( !exists $orig_cols->{$new_del_index_col} ) {
+         if ( !$orig_tbl->{del_index} ) {
+            die "The new table index $new_tbl->{del_index} would be used "
+               . "for the DELETE trigger, but it uses column "
+               . "$new_del_index_col which does not exist in the original "
+               . "table and the original table does not have a PRIMARY KEY "
+               . "or a unique index to use for the DELETE trigger.\n";
+         }
+         print "Using original table index $orig_tbl->{del_index} for the "
+            . "DELETE trigger instead of new table index $new_tbl->{del_index} "
+            . "because the new table index uses column $new_del_index_col "
+            . "which does not exist in the original table.\n";
+         $del_tbl = $orig_tbl;
+         last;
+      }
+   }
+
+   {
+      my $del_cols
+         = $del_tbl->{tbl_struct}->{keys}->{ $del_tbl->{del_index} }->{cols};
+      PTDEBUG && _d('Index for delete trigger: table', $del_tbl->{name},
+         'index', $del_tbl->{del_index},
+         'columns', @$del_cols);
+   }
+
    # ########################################################################
    # Step 3: Create the triggers to capture changes on the original table and
    # apply them to the new table.
@@ -8412,6 +8467,7 @@ sub main {
       create_triggers(
          orig_tbl     => $orig_tbl,
          new_tbl      => $new_tbl,
+         del_tbl      => $del_tbl,
          columns      => \@common_cols,
          Cxn          => $cxn,
          Quoter       => $q,
@@ -9536,11 +9592,11 @@ sub drop_swap {
 
 sub create_triggers {
    my ( %args ) = @_;
-   my @required_args = qw(orig_tbl new_tbl columns Cxn Quoter OptionParser);
+   my @required_args = qw(orig_tbl new_tbl del_tbl columns Cxn Quoter OptionParser);
    foreach my $arg ( @required_args ) {
       die "I need a $arg argument" unless $args{$arg};
    }
-   my ($orig_tbl, $new_tbl, $cols, $cxn, $q, $o) = @args{@required_args};
+   my ($orig_tbl, $new_tbl, $del_tbl, $cols, $cxn, $q, $o) = @args{@required_args};
 
    # This sub works for --dry-run and --execute.  With --dry-run it's
    # only interesting if --print is specified, too; then the user can
@@ -9569,8 +9625,8 @@ sub create_triggers {
    # unique indexes can be nullable.  Cols are from the new table and
    # they may have been renamed
    my %old_col_for    = map { $_->{new} => $_->{old} } @$cols;
-   my $tbl_struct     = $new_tbl->{tbl_struct};
+   my $tbl_struct     = $del_tbl->{tbl_struct};
-   my $del_index      = $new_tbl->{del_index};
+   my $del_index      = $del_tbl->{del_index};
    my $del_index_cols = join(" AND ", map {
       my $new_col  = $_;
       my $old_col  = $old_col_for{$new_col} || $new_col;

t/pt-online-schema-change/bugs.t

@@ -233,6 +233,34 @@ $sb->load_file('master', "$sample/del-trg-bug-1062324.sql");
       undef,
       "Delete trigger works after altering PK (bug 1062324)"
    );
+
+   # Another instance of this bug:
+   # https://bugs.launchpad.net/percona-toolkit/+bug/1103672
+   $sb->load_file('master', "$sample/del-trg-bug-1103672.sql");
+
+   ($output, $exit_status) = full_output(
+      sub { pt_online_schema_change::main(@args,
+         "$master_dsn,D=test,t=t1",
+         "--alter", "drop primary key, add column _id int unsigned not null primary key auto_increment FIRST",
+         qw(--execute --no-drop-new-table --no-swap-tables)) },
+   );
+
+   eval {
+      $master_dbh->do("DELETE FROM test.t1 WHERE id=1");
+   };
+   is(
+      $EVAL_ERROR,
+      "",
+      "No delete trigger error after altering PK (bug 1103672)"
+   ) or diag($output);
+
+   $row = $master_dbh->selectrow_arrayref("SELECT * FROM test._t1_new WHERE id=1");
+   is(
+      $row,
+      undef,
+      "Delete trigger works after altering PK (bug 1103672)"
+   );
+
 }
 
 # #############################################################################

t/pt-online-schema-change/samples/del-trg-bug-1103672.sql

@@ -0,0 +1,20 @@
+drop database if exists test;
+create database test;
+use test;
+
+CREATE TABLE `t1` (
+  `id` int(10) unsigned NOT NULL,
+  `x` char(3) DEFAULT NULL,
+  PRIMARY KEY (`id`)
+) ENGINE=InnoDB;
+
+INSERT INTO t1 VALUES
+  (1, 'a'),
+  (2, 'b'),
+  (3, 'c'),
+  (4, 'd'),
+  (5, 'f'),
+  (6, 'g'),
+  (7, 'h'),
+  (8, 'i'),
+  (9, 'j');